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The impact of a history of asthma on long-term outcomes of people with newly diagnosed chronic obstructive pulmonary disease: a population study

Kendzerska T, To TM, Aaron SD, Lougheed MD, Sadatsafavi M, FitzGerald JM, Gershon AS; Canadian Respiratory Research Network. J Allergy Clin Immunol. 2017; 139(3):835-43. Epub 2016 Sep 15.

Background — Little is known about the natural history of chronic obstructive pulmonary disease (COPD) that has developed from airway remodelling due to asthma, as compared to other COPD phenotypes.

Objective — We compared long-term health outcomes of individuals with COPD with and without a history of asthma in a population-based cohort study.

Methods — All individuals with physician-diagnosed COPD between ages 40 and 55 from 2009 and 2011 were identified and followed until March 2013 through provincial health administrative data (Ontario, Canada). The exposure was a history of asthma at least two years before the diagnosis of COPD to ensure it preceded of COPD. The hazards of COPD-, respiratory- and cardiovascular (CV) - related hospitalizations and all-cause mortality were compared between groups using a Cox regression model controlling for demographic characteristics, comorbidities and level of health care.

Results — Among 9,053 patients with COPD, 2,717 (30%) had a history of asthma. Over a median of 2.9 years, 712 (8%) individuals had a first COPD hospitalization, 964 (11%) - a first respiratory-related and 342 (4%) – a first CV-related hospitalization, and 556 (6%) died. Controlling for confounding, a history of asthma was significantly associated with COPD and respiratory-related hospitalizations (HR = 1.53, 95% CI: 1.29-1.82 and HR = 1.63, 95%CI: 1.14- 1.88, respectively), but not with CV-related hospitalizations or all cause mortality. Additional analyses confirmed these findings were not likely a result of unmeasured confounding or misclassification.

Conclusions — Middle-aged individuals with physician-diagnosed COPD and a history of asthma had a higher hazard of hospitalizations due to COPD and other respiratory diseases than those without.

Keywords: Asthma Chronic obstructive pulmonary disease Chronic diseases and conditions Respiratory diseases